[Diffraction halo]

Diffraction haloproduced by a coarse specklepattern transparency placed in thefocal plane of a helium-neonlaser, photographed by I MAndrews and M H Dossett ofIBM United Kingdom Laboratories,Hursly Park. This photographwas taken during the settingup of equipment for analysingspeckle pattern photographs,during measurements of the inplanestrain of a component. Thissuccessful technique can measuredisplacements down to a fractionof 0'001 in, without any contactbeing made with the object.